"Breakout force" (yet another question on this)

[SmallChange]

There are a number of references around, including threads here, that explain that breakout force or rollback force is the maximum force a loader can exert at the lip of the bucket by curling with it against the ground, as opposed to the smaller lifting force exerted by the loader arms with the bucket above the ground. Obviously, a claw hammer can pull a nail up with more force in prying mode than if you just try to pull the whole hammer up; that's the whole point of having a claw.

But I *still* don't get what my tractor specs mean:

Breakout force @ pivot pin: 1196.0 kg (2636.7 lb)
Bucket rollback force at ground level: 1234.0 kg (2720.5 lb)

The rollback force listed sounds like my above explanation of either term. But what is the breakout force being described here? There's no vertical motion at the pivot pin, it's a pivot (right?). I see the two forces are very close, but, what are they talking about?

I'm mostly just curious, but can anybody help me understand?

----------------

Here are some examples of the definition of breakout force I've found elsewhere (as you can see they vary widely):

"Breakout force is the force available to lift the FEL at the bottom of the pile"

"Breakout force is where any cylinder at power can no longer repond"

"It is the maximun force the bucket can curl at the cutting edge using the curling function"

"the maximum amount of upward force the FEL can generate using all of it's hydraulic circuits combined"

"Break out force is the weight that the bucket can curl or roll back"

"it's the sum off all cylinders available power at any one time, independant of the direction and axis of motion"

"bucket breakout is the curl and regular breakout was measured at the pivot where there would be no curl"

"Breakout force is probably best described as the amount of force or pressure (indicated in lbs per sq inch) required to free an object or load from the material it is surrounded or imbedded in." [Note they are saying it isn't a property of the machine, it's a property of the load]

"Technically (ISO or International Standards Org.), it's the maximum upward force in kN measured 100mm (or ft/lbs and 4" aft) of the cutting edge, achieved by the bucket cylinder(s), that is, the curl function, or in geometric terms the rolling moment around the bucket hinge."

 

[WranglerX]

Good question, I need to have better understanding also.....

Dale

 

[Zebrafive]

It appears your manufacture is calling boom cylinders breakout force and bucket cylinders rollback force.


I would NOT say it's maximum force of all hydraulics combined. Hydraulics will do the easiest load first, not combine forces.

 

[jjp8182]

So I had to look at my loader manual to confirm my recollection and here's what I found:

Bucket rollback force varies with lift arm height. Looking at the charts the peak rollback force actually occurs around 500mm, with the rollback at ground height being a bit less.

So there would be a difference between the ISO definition of maximum upward force and ground level rollback force. I suspect this is due to the geometry of the loader.

As for the pivot pin vs other measurements, I'm pretty sure that's done to remove the distance part of the equation. Rollback force is technically a force applied at a distance from a point of rotation which means it's really a torque. ....so I'd suspect the breakout force at the pivot pin is most likely the force the hydraulic cylinders are capable of creating at their attachment point to create a rotational force around the pivot pin. Though I'm not entirely entirely sure on that, as it seems there are often different definitions used between different companies/organizations.

So in other words engineering might be an endeavor filled with precision, but communicating those engineering results to others who weren't involved in the work rarely seems to be..... :confused2:

 

[ericm979]

It's purely the lifting force of the loader from the ground (or at the bottom of it's travel which might be slightly below ground level). The loader is strongest at the bottom of it's travel.

Here's the ISO 14397 definition of breakout force:
https://www.iso.org/obp/ui/#iso:std:iso:14397:-2:ed-2:v1:en


maximum sustained upward vertical force, in newtons, generated at a point 100 mm behind the leading edge of the bucket of a loader, or behind the foremost point of the cutting edge for a loader having a bucket with an irregular (pointed, curved, etc.) cutting-edge shape, by a lift or tilt cylinder, with the bottom of the bucket's cutting edge parallel to, and not more than 20 mm above, the ground reference plane

Of course ISO measures it at a different point than "at the pins" because they're ISO, but that's just geometry. (side note: where is 'at the pins' on a SSQA that's permanently fixed on the loader? the plate face?)

 

[Industrial Toys]

To me, it's a combination of machine traction, bucket force and loader lifting capacity. It never ceases to amaze me, how much power it takes to shove a thin steel edge into a hard pile. Yet you have no trouble slicing dep into flat ground, mostly when you don't intend to.

 

[SmallChange]

It appears your manufacture is calling boom cylinders breakout force and bucket cylinders rollback force.


I would NOT say it's maximum force of all hydraulics combined. Hydraulics will do the easiest load first, not combine forces.

Well, it isn't that. Boom cylinders give the force called out one line above in the specs. All three of the force specs are:

Lift capacity to maximum height @ pivot pin 726.0 kg (1600.6 lb)
Breakout force @ pivot pin 1196.0 kg (2636.7 lb)
Bucket rollback force at ground level 1234.0 kg (2720.5 lb)

There is a whole lot of stuff in the manual I could have posted.

 

[SPYDERLK]

It's purely the lifting force of the loader from the ground (or at the bottom of it's travel which might be slightly below ground level). The loader is strongest at the bottom of it's travel.

Here's the ISO 14397 definition of breakout force:
https://www.iso.org/obp/ui/#iso:std:iso:14397:-2:ed-2:v1:en


maximum sustained upward vertical force, in newtons, generated at a point 100 mm behind the leading edge of the bucket of a loader, or behind the foremost point of the cutting edge for a loader having a bucket with an irregular (pointed, curved, etc.) cutting-edge shape, by a lift or tilt cylinder, with the bottom of the bucket's cutting edge parallel to, and not more than 20 mm above, the ground reference plane

Of course ISO measures it at a different point than "at the pins" because they're ISO, but that's just geometry. (side note: where is 'at the pins' on a SSQA that's permanently fixed on the loader? the plate face?)

THIS ^ ^

EXCEPT - - Breakout motion is not vertical. At ground level The motion of the bucket is up and forward. If you are pushing at the same time as you are lifting a component of that push fights the breakout force. The tractor must be free to move back somewhat in order to not offset breakout force available.​

 

[rScotty]

Breakout force @ pivot pin: 1196.0 kg (2636.7 lb)
Bucket rollback force at ground level: 1234.0 kg (2720.5 lb)

The rollback force listed sounds like my above explanation of either term. But what is the breakout force being described here? There's no vertical motion at the pivot pin, it's a pivot (right?). I see the two forces are very close, but, what are they talking about?

I'm mostly just curious, but can anybody help me understand?

I don't see the problem. The specs you quote are exactly how I would describe it. A force doesn't require any motion. It's just a force. You weigh the same standing or moving.

Breakout force at the pin is the vertical lifting force of the loader arms provided by the loader arm cylinders.
Breakout force varies with the position of the loader arms. In this case it would be when the bucket is flat on the ground.

Rollback force at the bucket tip is the rotational force provided by the bucket cylinder(s) as the bucket tip rotates around the pivot pin. It varies with the bucket dimensions.

Lift force at full height is a measure of the vertical force provided by the loader arm cylinders - same cylinders and same pressure as the breakout force - but it gives a different number since the horizontal distance from the loader cylinder mounts to the pivot pin is now different.

Hope this helps.
rScotty

 

[mikester]

Just think of breakout force as the ability to curl loads. If you have a long bucket or are using forks you will want more breakout force.

Tractor specs seem to be made by sales guys who only want one easy number to quote from. If you have a light machine over optimistic specs do nothing for the operator.

When you look a commercial construction equipment specs they tend to include things like safe working loads at max height and in full turns. When OHSA gets involved then manufacturers talk about safety and operating capacity. When selling to non-commercial types its all about selling the sizzle to satisfy guys wanting bragging rights for their toy that sits in the driveway most of the time.

Bottom line is if you are a homeowner consumer your perspective will be limited and you have to take what the sales guy is pushing worth a grain of salt...you are small fry and a one time sale, move aside now please.

 

[Zebrafive]

Well, it isn't that. Boom cylinders give the force called out one line above in the specs. All three of the force specs are:

Lift capacity to maximum height @ pivot pin 726.0 kg (1600.6 lb)
Breakout force @ pivot pin 1196.0 kg (2636.7 lb)
Bucket rollback force at ground level 1234.0 kg (2720.5 lb)

There is a whole lot of stuff in the manual I could have posted.

So which cylinders do you think are making the force in line two above? Boom cylinders or bucket cylinders? Both?
I agree boom cylinders for line one.
I also say boom cylinders for line two.
Bucket cylinders for line three

 

[rScotty]

So which cylinders do you think are making the force in line two above? Boom cylinders or bucket cylinders? Both?
I agree boom cylinders for line one.
I also say boom cylinders for line two.
Bucket cylinders for line three

That's correct.
rScotty

 

[SmallChange]

So which cylinders do you think are making the force in line two above? Boom cylinders or bucket cylinders? Both?
I agree boom cylinders for line one.
I also say boom cylinders for line two.
Bucket cylinders for line three

Oh. I think I see what you mean. Yes, that makes sense. Thanks! Though I'm still trying to make sense of another post, too....

 

[SmallChange]

It's purely the lifting force of the loader from the ground (or at the bottom of it's travel which might be slightly below ground level). The loader is strongest at the bottom of it's travel.

Here's the ISO 14397 definition of breakout force:
https://www.iso.org/obp/ui/#iso:std:iso:14397:-2:ed-2:v1:en


maximum sustained upward vertical force, in newtons, generated at a point 100 mm behind the leading edge of the bucket of a loader, or behind the foremost point of the cutting edge for a loader having a bucket with an irregular (pointed, curved, etc.) cutting-edge shape, by a lift or tilt cylinder, with the bottom of the bucket's cutting edge parallel to, and not more than 20 mm above, the ground reference plane

Of course ISO measures it at a different point than "at the pins" because they're ISO, but that's just geometry. (side note: where is 'at the pins' on a SSQA that's permanently fixed on the loader? the plate face?)

Ah, I think I'm getting it. Thank you. This isn't necessarily the maximum possible upward force, because they are constraining that the bucket is slightly elevated with a horizontal bottom, so it's not in contact with the ground anyplace and therefore it's not prying like a claw hammer. But you are allowed to use any combination of loader arm and bucket curl cylinder. They aren't specifying any limitation in cylinder choice. Like you say. Purely the lifting force from slightly above the ground. (Note, though, it can't be from slightly below ground level, it's with 20 mm clearance above the ground.)

NONE of the lines in my manual's spec list is exactly this. I'm guessing the middle line out of the three would come the closest.

 

[rScotty]

Ah, I think I'm getting it. Thank you. This isn't necessarily the maximum possible upward force, because they are constraining that the bucket is slightly elevated with a horizontal bottom, so it's not in contact with the ground anyplace and therefore it's not prying like a claw hammer. But you are allowed to use any combination of loader arm and bucket curl cylinder. They aren't specifying any limitation in cylinder choice. Like you say. Purely the lifting force from slightly above the ground. (Note, though, it can't be from slightly below ground level, it's with 20 mm clearance above the ground.)

NONE of the lines in my manual's spec list is exactly this. I'm guessing the middle line out of the three would come the closest.

I think I see your problem. Yes, the rotation of the bucket DOES add fractionally to the pure vertical lift force at the pivot if you actuate both sets of cylinders at once. You are correct in that.

But that's not how the manual's spec list has described it. Look again. By definiing line two to be measured at the pivot point for the bucket, the length of the moment arm for the bucket cylinder forces is reduced to to zero. So the bucket contribution to lift is zero simply because they have defined the bucket out of the boom lifting calculations. We are only left with the vertical component of the lifting forces that are provided by the boom cylinders. Using the specs given - and their own selection of pivot points - the vertical lifting forces are simply the vertical component of the boom cylinder lifting forces around the boom pivots. Everything else goes to zero.
rScotty

It comes down to defining the pivot point. To reiterate....as defined, the bucket forces are zero for boom lift calcs becasuse of where they placed the bucket pivot point and I agree that is valid.
Now I think your question is this: Is it reality to put that pivot point where they did? Well, not completely..... and I think that is what is hanging you up. But it's the simplest way to calculate the forces - and arithmatically it is elegant. It works perfectly well.
If you do want to calculate the contribution of the bucket rotation to the lift, you have to move the bucket calculations to a different pivot point. That way the vertical component of the bucket rotation doesnt become zero. Then simply add the vertical components. By defining the pivot where they have, they have made these other calculations possible and even easily done if needed.
rScotty

 

[SmallChange]

I think I see your problem. Yes, the rotation of the bucket DOES add fractionally to the pure vertical lift force at the pivot if you actuate both sets of cylinders at once. You are correct in that.

But that's not how the manual's spec list has described it. Look again. By definiing line two to be measured at the pivot point for the bucket, the length of the moment arm for the bucket cylinder forces is reduced to to zero. So the bucket contribution to lift is zero simply because they have defined the bucket out of the boom lifting calculations. We are only left with the vertical component of the lifting forces that are provided by the boom cylinders. Using the specs given - and their own selection of pivot points - the vertical lifting forces are simply the vertical component of the boom cylinder lifting forces around the boom pivots. Everything else goes to zero.
rScotty

It comes down to defining the pivot point. To reiterate....as defined, the bucket forces are zero for boom lift calcs becasuse of where they placed the bucket pivot point and I agree that is valid.
Now I think your question is this: Is it reality to put that pivot point where they did? Well, not completely..... and I think that is what is hanging you up. But it's the simplest way to calculate the forces - and arithmatically it is elegant. It works perfectly well.
If you do want to calculate the contribution of the bucket rotation to the lift, you have to move the bucket calculations to a different pivot point. That way the vertical component of the bucket rotation doesnt become zero. Then simply add the vertical components. By defining the pivot where they have, they have made these other calculations possible and even easily done if needed.
rScotty

I think I got it. There's an ISO definition of breakout force, and there's a different definition my owner's manual uses. Not the same thing, but probably the numbers are pretty close. And there's yet another force that one could conceivably create, by resting the bucket on the ground and curling it with a prying motion.

I'll tell you what was hanging me up -- seeing "breakout force" defined as the bucket force you can get with the curling cylinders, and in other places seeing "breakout force" defined at the pivot pin, where -- as you point out -- there's no motion when curling. These are two contradictory uses of "breakout force". And, it's funny that the ISO definition isn't EITHER of these two.

 

[rScotty]

I think I got it. There's an ISO definition of breakout force, and there's a different definition my owner's manual uses. Not the same thing, but probably the numbers are pretty close. And there's yet another force that one could conceivably create, by resting the bucket on the ground and curling it with a prying motion.

I'll tell you what was hanging me up -- seeing "breakout force" defined as the bucket force you can get with the curling cylinders, and in other places seeing "breakout force" defined at the pivot pin, where -- as you point out -- there's no motion when curling. These are two contradictory uses of "breakout force". And, it's funny that the ISO definition isn't EITHER of these two.

Yep, I think you are right on the cause of the hang up. There's a lot of various codes and standards out there for manufacturers who either want to use them or has some reason to do so.
Such "Standards" can be contradictory or even political.....no surprise there

Looking at that link you posted showing how ISO wrestled with defining breakout force, I gotta say I prefer the way your tractor manufacturer did it.
To me, New Holland made the right choice to define their loader specs using their own in house definition and standard.

enjoyed it,
rScotty

 

[ericm979]

I read the ISO spec as measuring the same way you'd measure at the pins- purely the lifting force- except correcting for the load's center of gravity being a ways ahead of the pins. That's how most 3pt lift specs are stated, i.e. 24" past the end of the lift arms or similar. That gives a more realistic measurement, because of course the 3pt implement or load on the loader is not centered at the lift arms or at the loader pins- it's farther out and thus has more leverage on the loader or 3pt, reducing the lift capacity. It's why you'll see companies like Kubota report loader lift capacities at a fixed distance in front of the pins (and I think they also report it at the pins for competitive purposes).

ISO being ISO they made the definition hard to understand and dependent on the depth of the bucket, which would becorrect mechanically if they did it right but confuses the issue. (I've spent a lot of my career both implementing from and writing standards).

Where are the pins on a SSQA loader?

 

[searcyfarms]

LOL, it doesnt matter what force or lift capacity you buy it will never be as much as you want/need at given time - you can read specs and evaluate them all you want but honestly, there are so many other variables that will determine what you can lift and where - the object, the angle of ground, the position of tractor, what kind of surface you are on, i dont look at specs i look at what i know i can do when trying to manipulate what i want to move and where i want/need to move it to. Do i need to scoot it, do i need to lift it 3 feet, do i need to lift a corner of it and rotate it, how much room do i have, is it slick out, is it on concrete, a spec looses it value when you take all those things into consideration. You may have a certain spec but you might not be able to use it nor will it do what you need at the time.

 

[rScotty]

ISO being ISO they made the definition hard to understand and dependent on the depth of the bucket, which would becorrect mechanically if they did it right but confuses the issue. (I've spent a lot of my career both implementing from and writing standards).

Where are the pins on a SSQA loader?

The pins are in the same location at the ends of the loader arms. For calculations, think of the the SSQA as being part of the back of the bucket. With SSQA the bucket weighs a little more and the cutting edge of the bucket is a few inches farther from the bucket pivot.
rScotty